Pallet loader

ABSTRACT

The invention concerns an improved device in pallet loaders, comprising an upright frame (1) and a pair of horizontal lifting fork members (2) which may be raised and lowered together with said frame (1) by means of a lifting mechanism. The lifting fork members (2) are equipped at their outermost end with one support wheel (4) each, which wheels are attached to an articulated arm (14) arranged to be pivoted downwards. The frame (1) and the lifting fork members (2) may be raised and lowered by means of a rack (6) which is connected via a cable, wire on chain (10) to an articulated, two-armed rocker arm (13). In turn, the latter is connected to the articulated arm (14) by means of a traction rod (15) which is associated with the arm (14). Upon upwards motion of the rack (6) and thus of the frame (1) a pulling force on the cable (10) will be transferred via the rocker arm (13) and the traction rod (15) to the articulated arm (14), which then swings downwards, thus raising the lifting fork members (2).

This Application is a 371 of PCT/SE96/00592 (May 07, 1996)

The invention concerns an improved pallet loader comprising an uprightframe and a pair of horizontal lifting fork members projecting from theframe and being vertically displaceable together with said frame bymeans of a hoisting mechanism incorporated in the pallet loader. Eachfork member is equipped at its free end opposite the frame with asupport wheel in contact with a supporting surface.

Pallet loaders of this kind designed to lift and transport pallet loadsare generally equipped with an hydraulically operated hoistingmechanism. This kind of mechanism is a versatile construction that iseasy to manipulate, also when the loads are comparatively heavy.

The construction does, however, suffer from certain drawbacks. Forinstance, it is difficult to maintain its valves and couplings in acompletely sealed condition for any length of time. Consequently, oilleakages occur from time to time, which is a considerable nuisance,particularly when the pallet loader is used in a "tidy" environment, forinstance when driven on sensitive surfaces, such as wall-to-wall carpetsand the like. In order to reduce the risk of soiling of or even damageto the supporting surface oil leakages may be prevented by ensuringfrequent servicing of the pallet loader lifting mechanism hydraulics. Asalways, extensive servicing does, however, involve not insignificantexpenses.

The subject invention suggests a purely mechanical lifting mechanism foruse in pallet loaders, by means of which the problem outlined above isentirely eliminated while at the same time it provides an improved gearratio for a given size of pallet loader than the hydraulic liftingmechanism, allowing the goods to be handled quicker and moreefficiently. The characterizing features of the device in accordancewith the invention will appear from the appended claims.

The invention will be described in closer detail in the following withreference to the accompanying drawings, wherein

FIG. 1 is a vertical sectional view through a pallet loader inaccordance with the invention, the loader being shown in a lowerposition,

FIG. 2 is a similar view but showing the pallet loader in a liftedposition,

FIG. 3 is a vertical sectional view on a larger scale of a part of thelifting mechanism, and

FIG. 4 shows the lifting mechanism in a perspective exploded view and ona larger scale.

The pallet loader consists of an upstanding frame portion 1 and a pairof horizontal lifting fork members 2 projecting from the frame. At itsrear, the pallet loader is provided with a couple of larger support andsteering wheels 3 and at its front, at the forward ends of the forkmembers, with a pair of smaller support wheels 4.

Intermediate the rear support and steering wheels 3 a vertical hollowcylinder 5 is mounted. Inside the latter, a rack 6 is arranged to beraised and lowered, and the frame portion 1 is supported against theupper end of the rack which projects past the cylinder 5. A couple oftransverse stays 8 extend between the frame portion 1 and a locatingbearing 7 surrounding the hollow cylinder 5.

In the version illustrated in the drawing figures, the rack 6 isconfigured as a pipe. From a lower point of attachment 9, below the rack6, a cable, wire, chain 10 or the like extends through the rack to oneend of a two-armed rocker arm 13, via a first pulley 11 and a secondpulley 12. A traction rod 15 extends between the opposite end of therocker arm 13 and an articulated arm 14 on which the support wheel 4 ismounted. The traction rod 15 is connected to the articulated arm 14 in apivot 16 which is spaced somewhat from the pivot pin 17 on which thearticulated arm 14 is pivotally mounted, in order to create a momentwhen a pulling force is exerted on the traction rod 15.

In addition, the pallet loader is provided with a lever 18 and with anoperating handle 19 with a manually operated control means 20 thereon,by means of which the lifting mechanism may be actuated with the aid ofan operating rod 21 extending through the lever 18. This arrangementwill be described in closer detail in the following. The lever 18 isconnected with a rod-shaped pinion 22 which engages the rack 6.

The lifting mechanism operates in the following manner. When the lever18 is swung downwards in the direction indicated by arrow 23, see FIG.2, the rod-shaped pinion 22 drives the rack 6 somewhat upwards, out ofthe cylinder 5, thus forcing the frame portion 1 and the lifting forkmembers 2 to take part in this upwards movement. Because the pulleys 11and 12 move together with the frame portion 1, a pulling force isexerted on the wire 10, etcetera, urging the rocker arm 13 to rock inthe direction of arrow 24. A pulling force is then generated, acting onthe traction rod 15 in the direction of arrow 25, with the result thatthe articulated arm 14 pivots downwards, in consequence whereof thesupport wheel 4 will abut against the supporting surface 26 on which thepallet loader rests. Because of the lifting movement described, theforwards ends of the lifting fork members will take part in the liftingmovement of the rest of the pallet loader.

With reference to FIG. 4 the function of the lifting mechanism will bedescribed in closer detail. The lever 18 is provided with a couple ofangle plates 27, by means of which the lever 18 is freely rotatableabout the rod-shaped pinion 22. At the adjacent end of the rod pinion22, as seen in the drawing, a free wheel 28, around which a brake lining29 is passed, is securely attached. The brake lining 29 is attached tothe angle plate 27 so as to follow the pivotal movement thereof. Bymeans of an eccentric element 30 the brake lining 29 is tightened aboutthe free wheel. A set screw 31 is provided to adjust the tighteningforce of the brake lining 29.

The free wheel 28 operates in the following manner. When the lever 18 isswung downwards, its pivotal movement is transferred via the angle plate27, the friction lining 29 and the free wheel 28 which then urges thepinion 22 to turn anti-clockwise as seen in FIG. 4, forcing the ratchet6 to move upwards, out of the hollow cylinder 5. Upon return movement ofthe lever 18 the free wheel 28 runs freely on the pinion 22.

The opposite end of the rod-shaped pinion 22 supports a ratchet wheel 32securely attached thereto and in engagement with a wedge-shaped catch33, the latter being mounted on a rotational shaft 34 which is biased bya spring 35 to turn the catch wedge 33 to its blocking position,engaging the ratchet wheel 32. As the lever 18 performs its returnmovement mentioned above, the ratchet wheel 32 thus will prevent therod-shaped pinion 22 from taking part in this movement and again lowerthe ratchet 6.

By means of the operating rod 21 the manually operated control means 20is connected to a link 36 which is mounted on the same pivot shaft 37 asthe eccentric element means 30. In addition, via flexibleinterconnection means 38 the link 36 is attached to the rotational shaft34.

The manual control 20 allows the mechanism to be set in three differentpositions, viz. a lower position when the link 36 is displaced in thedirection of arrow 39, a middle position illustrated in the drawing, andan upper position when the link 36 is displaced in the direction ofarrow 40. In the lower position, the eccentric element 30 has beenturned inwards, to a braking position in engagement with the brakelining 29. In this position, the lifting mechanism is effective to raisethe lifting fork members 2. Every time the lever 18 is pulled downwards,the ratchet wheel 32 thus moves past the wedge-shaped catch 33 and uponeach return movement of the lever 18, the wedge-shaped catch 33 movesinto a blocking position while at the same time the braking device andthe free wheel 28 travel freely above the rod-shaped pinion 22 and thusfollow the angle plate 27 in its return movement.

When the link 36 is moved to the middle position, the interconnectionmeans 38 is slightly stretched. When the operating handle 19 and thelever 18 are pulled downwards, the interconnection means 38 will bestretched, releasing the catch 33 from its engaged blocking position.However, the eccentric element 30 has been moved over a short distanceonly, for which reason the brake mechanism still is tightened. By meansof pulling the manual control 20 in this situation and thus moving thelink 36 in the direction towards the upper position, i.e. in thedirection of arrow 40, the braking mechanism may be releasedsuccessively, making the lifting fork members 2 to be lowered towardsthe support 26 at a slower or quicker pace.

By the provision of a bent, flexible interconnection means 38 a fourthset position of the lifting mechanism becomes possible. For when themanual control means 20 is pulled without the lever 18 also being swungdownwards, the eccentric element 30 will be turned away from its lockingposition but the interconnection means 38 will only be straightened andthus not disengage the wedge-shaped catch 33. In this position, thelever 18 will be freely movable, which facilitates actuation andadvancement of the pallet loader.

The invention is not limited to the embodiment described and illustratedbut could be varied in several ways within the scope of the appendedclaims. Instead of the ratchet wheel 32, for instance, a free wheelcould be placed also at this side, acting in the opposite direction tofree wheel 28 and being formed with only one or possibly a few recessesin which the wedge catch 33 may engage for locking purposes. Thissolution eliminates the rattling noise created by the wedge catch 33 asit runs over the teeth of the ratchet wheel 32.

I claim:
 1. An improved device in pallet loaders, comprising an uprightframe (1), and a pair of horizontal lifting fork members (2) projectingfrom the frame (1) and being vertically displaceable together with saidframe (1) by means of a hoisting mechanism incorporated in said device,each fork member (2) equipped at its free end opposite the frame (1)with a support wheel (4) in contact with a supporting surface (26) andmounted on an articulated arm (14) which is hingedly mounted on a pivotpin (17) on the lifting fork members (2), whereby said arm (14) may bepivoted downwards away from said members (2) to increase the distance ofsaid members to the supporting surface (26), the hoisting mechanismcomprising a rack (6) which is arranged to be raised and lowered insidea vertical hollow cylinder (5) and which is connected to the frame (1)in such a manner as to make the latter and the lifting fork members (2)take part in its upwards and downwards movements, and a two-armed rockerarm (13) which is pivotally connected to the frame (1) and one end ofwhich is attached to the articulated arm (14) by means of a rod (15),the latter being connected to the articulated arm (14) in a pivot (16)spaced from the pivot pin (17), characterized in that the rod (15) is atraction rod and that the rocker arm (13) at the end opposite the rod(15) is connected to a line (10) extending, via a pair of pulleys (11,12) mounted on the frame (1), through the rack (6) to a point (9) ofattachment, and in that the rack (6) is arranged, when moving upwards,to lift the frame (1) while at the same time bringing the line (10) torock the rocker arm (13), the latter, in turn arranged, when rocked, bymeans of traction to urge the rod (15) to pivot the articulated arm (14)downwards and thus to lift the lifting fork members (2) off thesupporting surface (26).
 2. A device as claimed in claim 1, whereby therack (6) is vertically displaceable by means of a rotatable rod-shapedpinion (22) which engages the rack (6) characterized in that a lever(18) is mounted on the rod-shaped pinion (22) for free pivotablemovement thereon, on which lever (18)a braking mechanism (29, 30, 31) issecured so as to follow the movements of the lever (18), and in that oneend of the rod-shaped pinion (22) supports a free wheel (28) cooperatingwith the pinion (22) and the braking mechanism (29, 30, 31) in such amanner that the braking mechanism (29, 30, 31), when applied and upon alever movement to lift the lifting fork members (2), forces the freewheel (28) to rotate the pinion (22) to lift the ratchet (6), whereas alever movement in the opposite direction is not transferred to therod-shaped pinion (22), and in that on the opposite end of the pinion(22) is securely mounted a ratchet wheel (32), in which may engage awedge-shaped catch (33) arranged to prevent rotational movement of therod-shaped pinion (22) in the said opposite direction.
 3. A device asclaimed in claim 1, characterized in that a manual control means (20)for resetting the hoisting mechanism is coupled to a link (36) which isarranged via a manual control means (20) to turn a shaft (37), on whichis securely mounted a means (30) for the application and the release ofa braking mechanism (29, 30, 31).
 4. A device as claimed in claim 3,characterized in that the braking mechanism consists of a lining (29)applied about the free wheel (28), and in that the means for theapplication and the release of the braking mechanism consists of aneccentric element (30) in abutment against an end portion of the brakelining (29) and arranged for turning movement on the shaft (37) in adirection towards and outwardly away from said end portion.
 5. A deviceas claimed in claim 4, characterized in that a set screw (31) arrangedto regulate the force of application of the brake lining (29) againstthe free wheel (28) by means of the eccentric element (30) abuts againstthe opposite end portion of the brake lining (29).
 6. A device asclaimed in claim 1, characterized in that a wedge-shaped catch (33) issecurely mounted on a rotary shaft (34) which is connected to a link(36), and may be pivoted from its engaged blocking position against theaction of a spring means (35) as a result of a manual control means (20)displacing said link (36).
 7. A device as claimed in claim 6,characterized in that the link (36) is connected to the rotary shaft(34) by means of a flexible, elastic interconnection means (38).